Roofing and the like



Patented July 7, 1942 ROOFlNG AND THE LIKE Richard A. Wilkins, Rome, N. Y., assignor to Revere Copper and Brass Incorporated, Rome, N. Y., a corporation of Maryland No Drawing. Application June 3, 1941, Serial No. 396,431

Claims.

My invention relates to roofing and the like, and particularly to improvements in the roofing forming the subject matter of applicant's patents No. 2,240,447, issued April 29, 1941, No. 2,244,093, issued June 3, 1941, No. 2,249,698, issued July 15, 1941, and No. 2,261,909, issued November 4, 1941.

As pointed out in the above mentioned patents, the material heretofore commonly employed for copper roofing, sheathing, and other exposed protective coverings for buildings has been thin rolled sheets of highly refined copper. Further, in refining copper for these purposes it has heretofore always been the practice of producers thereof to remove so far as possible all impurities so as to secure as pure 2. copper as possible. The known high resistance of pure copper generally to chemical corrosion, and the observed fact that impurities commonly found in rolled copper commonly tend to make it less ductile in both the hot and cold rolled conditions, commonly more difficult to produce by either hot or cold rolling, and commonly cold short in the sense that it tends to crack when bent or otherwise cold worked, have caused pure copper heretofore to be considered the most satisfactory commercially available material for light weight metal roofing and the like. In fact during the past forty years copper roofing has for these reasons been made almost exclusively of electrolytically refined copper, which commonly is 99.9% pure copper.

Nevertheless it is a frequently observed fact that copper roofing, even when substantially 100% pure electrolytically refined copper, often fails in use, being subject to cracking sufiicient to render it non-waterproof. Heretofore it was to, applicant has found that the failure of copper roofing and the like heretofore has not been correctly understood. This material, he has found, does not fail primarily by reason of the cyclic stresses to which it is subjected when in use, as heretofore believed, but, strangely'enough, primarily by reason of a heretofore wholly unsuspected type of corrosion which occurs when this highly pure copper is exposed to an atmosphere contaminated by wind borne products of combustion of modern domestic and industrial fuel burning appliances and industrial atmospheres in general.

Applicant has found, that upon removing the patina and other accumulated corrosion products from copper roofing which has failed, the copper believed that these cracks were caused by mechanical fatigue resulting by reason of the cyclic stresses set up by alternate expansion and contraction of the copper roofing sheets under varying temperature conditions. For that reason builders heretofore have resorted to expensive roof constructions, and various expensive expedients such as corrugating the roofing and the employment of elaborately designed expansion joints, and the use of heavy gauge copper in the attempt to relieve or reduce the efiect on the roofing of these cyclic stresses and thereby eliminate so far as possible this form of failure. Although these attempts have been partially successful, the expense incidental thereto, and the many failures which actually have occurred in spite of these precautions, have seriously interfered with the general adoption of this otherwise very satisfactory roofing.

As pointed out in the patents above referred roofing surface thus exposed is characteristically pitted, instead of being in its smooth unpitted condition in which it originally left the rolling mill or the roofing showing a uniform decrease in thickness over its whole surface due to corrosion.

His investigations show that these pits are caused by the formation on the copper, when exposed to a contaminated atmosphere, of a film of corrosion products which is characterized by a lack of adhesion to the copper, a lack of tenacity in respect, to failure, and a tendency toward perviousness which allow the copper to be attacked locally rather than uniformly by the corrosive media and thereby result in the formation of sharply defined, inwardly pointed pits in the nature of notches. He has found that copper roofing so attacked rapidly fails when subjected to the cyclic stresses hereinbefore referred to by reason of the natural tendency of the stresses to be concentrated in the metal below the bottoms of the notch-like pits. As a result of this concentration of the stresses, the metal below the bottoms of the pits work hardens and the fatigue strength of the material is exceeded, and as a result the metal cracks at the pits.

Pure copper roofing applicant has found is comparatively sensitive to this notch effect, when caused by a combination of chemical corrosion and subjection to cyclic stresses, on account of the film which forms on it causing the pure copper to pit and the great sensitivity of pure copper to work hardening when cold worked.

The above mentioned patents point out that this type of failure of copper roofing as constructed from thin sheets, commonly from 0.003 to 0.03 inch in thickness, can be substantially entirely avoided by incorporating into the copper controlled amounts of arsenic, or antimony, or phosphorus, or both arsenic and antimony.

When proper amounts of any of the above mentioned substances are incorporated into the copper roofin it has been found that the surface of the roofing, after the patina or other accumulated products of corrosion are removed, is in an unpitted condition, any corrosion which has occurred being substantially uniformly distributed over its surface. It has also been found that the incorporation of any of these substances most markedly decreases the sensitivity of the copper to cold work hardening, and therefore any scratches, dents, or the like in the nature of notches which might be formed during the handling or installation of the roofing will not cause it to fail by notch effect. In other words, the action of any of these substances on the roofing is twofold: it prevents notches from being formed by corrosion and prevents the roofing failing by notch effect even if the notches are accidentally formed by mechanical means.

It has been found that the presence of proper amounts of these substances in the copper roofing produces on the roofing surface a corrosion film which is tenacious, adherent, impervious and non-hygroscopic, the film being comparably as ductile as the copper base material itself, thus permitting the roofing to be repeatedly bent without rupture of the film or interruption of its adherence to the copper. Thu this film effectively protects the underlying base material from contaminated air and moisture, and in this way effectively eliminates the possibility of the formation of the above mentioned notch-like pits, for any slight amount of corrosion which occurs will be uniformly distributed over the surface of the copper. Most importantly this film has the property of being self-healing in the sense that if for any reason its continuity is locally interrupted it will substantially immediately reform when subjected to corrosion and thus act to prevent substantial local corrosion at the interrupted regions which in a pure copper roofing would continue to corrode at an accelerated rate resulting in pitting at the point of interruption of the film.

It will be understood that the roofing i produced by first casting a slab of the copper containing small amounts of these other substances and rolling the slab to produce the copper roofing sheets, the same as in producing pure copper roofing sheets. It has been found that, under adverse conditions, in forming the cast slab the roofing consisting of copper with additions of either or both arsenic and antimony is liable to contain arsenic or antimony oxides or complex oxides of arsenic and antimony. Such oxides, if present, will be distributed between the crystals or so-called grain boundaries of the metal, and will seriously reduce the strength and ductility of the roofing, which strength and ductility are dependent upon the locking together of these crystals. On the other hand, the amount of phosphorus necessary to produce the above mentioned beneficial effects, if phosphorus alone is incorporated in the copper, is within the range of 0.1 to 1%, the maximum effects being secured with 0.4 to 0.6% phosphorus. Amounts of phosphorus, it has been found, in excess of about 0.2% tend to cause waste in casting the slab due to piping at the last poured portions thereof.

Applicant has found, that by incorporating into the molten metal amounts of phosphorus with either or both the arsenic and antimony, the

presence of oxides of these latter substances between the crystals of the metal is entirely avoided, with the result that the metal containing arsenic or antimony, or both, is rendered stronger and more ductile. He has also found that by adding with the arsenic or antimony, or both, a proper amount of phosphorus under that which will cause deleterious piping, the above mentioned film which forms on the roofing when subjected to atmospheric corrosion is much more tenacious, adherent and impervious than that which is formed when only phosphorus, or arsenic, or antimony, or arsenic and antimony are added, and at the same time the presence of oxides of either or both arsenic and antimony between the crystals is avoided.

The present invention therefore relates to an improved copper roofing which contains controlled amounts of phosphoru and metal of the group consisting of arsenic and antimony. The presence of as little as 0.001% phosphorus in the roofing will insure that the deleterious oxides of metal of this group are absent. By increasing this amount of phosphorus about fifty times to 0.05% the above mentioned marked improvement in the protective qualities is secured.

In respect to forming this film by the addition of phosphorus and metal of the group consisting of arsenic and antimony it is believed that initially the phosphorus causes copper phosphide to form on the surface of the roofing, while the arsenic and antimony cause metallic arsenic and antimony initially to form on the surface of the roofing, and that when exposed to atmospheric corrosion the copper phosphide immediately is converted to copper phosphate, while the arsenic and antimony are immediately converted to oxides of these, or, if both are present, a complex oxide of them. It has been found that both arsenic and antimony oxides are extremely resistant to destruction by atmospheric corrosion, and that the complex oxide of arsenic and antimony is more so, while copper phosphate, it has been found, is more resistant in this respect than any of the others. These oxides and the copper phosphate in the film it is believed are so combined either chemically or mechanically that the resulting film possesses its improved properties when compared to the properties of the film which would be formed if the copper contained arsenic, or antimony, or phosphorus, alone, or a combination of arsenic and antimony without phosphorus.

To secure best results, when incorporated with metal of the group consisting of arsenic and antimony, the maximum amount of phosphorus according to the present invention is about 0.2%, better results in minimizing piping being secured if the maximum does not exceed 0.15%. Above 0.2% phosphorus no marked improvement in the properties of the film is observed, and the wastage caused by the presence of phosphorus becomes objectionable. The amount of arsenic to be employed when no antimony is present may be from 0.02 to 1.5%, best results being secured within the range of 0.35 to 0.65% arsenic. The amount of antimony to be employed when no arsenic is present may be from 0.05 to 0.8%. When both arsenic and antimony are present the desired results will be secured when the arsenic is within the range of 0.1 to 0.8% and the anti mony within the range of 0.05 to 0.4%. The maximum effects, when both arsenic and antimony are present, will be secured with the arsenic within the range of 0.4 to 0.6% and the antimony within the range of 0.2 to 0.3%. Further,

when both arsenic and antimony are present, best results will be secured when the amount of arsenic is at least twice the amount of antimony.

Best results with the improved roofing ordinarily will be secured if the roofing does not contain impurities which tend to render it less malleable in the hot and cold conditions and thus tend to cause the hot or cold rolling or other working of the roofing during its fabrication to result in sub-microscopic surface cracks therein analogous in their effects to pits.

Among these deleterious substances are lead, bismuth, iron, nickel and sulphur, rather small amounts of all of which tend to make the copper roofing more difiicult to produce, and all of which tend to make the improved copper roofing approach the poor resistance of pure copper roofing to corrosion and its sensitivity to notch efiect, and thereby act to destroy the beneficial effects of the combination of phosphorus and metal of the group consisting of arsenic and antimony. The presence of such substances as cobalt, tin, silicon and zinc in substantial amounts had also best be avoided as they tend to increase the sensitivity of the copper roofing to work hardening and notch effect. It will thus be understood, that in the sense the copper roofing does not contain amounts of substances which substantially destroy the beneficial effects tended to be imparted by the combination of phosphorus and the metal of said group, the balance of the alloy aside from the phosphorus and metal of said group is essentially copper.

In making the roofing according to the invention the copper may be melted, and the other substances added to the melt in the form of binary copper-phosphorus, copper-arsenic, and copper-antimony alloys rich in phosphorus, arsenic and antimony, respectively. The molten metal may then be cast into slabs, which latter may be rolled into sheets of desired thickness by the usual mill process of rolling copper roofing sheets. Finally the rolled sheets may be annealed to the degree of softness that will best resist the cyclic stresses to which they are subjected when in use.

For convenience in terminology the article of manufacture according to the invention is termed roofing, it being understood that as used in the appended claims such term includes various shingles, sheathings, valleys, and like protective coverings for buildings, as well as what in a more limited sense is ordinarily termed roofing. Also it will be understood that the roofing according to the invention comprises sheet copper presenting an extensive external roofing surface, and may in this sense consist of a backing having an exterior sheet of copper as well as consist wholly of sheet copper.

I claim:

1. Roofing comprising sheet copper presenting an extensive external roofing surface, the copper being alloyed with such amounts of phosphorus and metal of the group consisting of arsenic and antimony as will cause the formation on said surface when exposed to atmospheric corrosion of a self-healing, adherent, protective film of compound containing phosphorus and metal of said group, while rendering the sheet copper less sensitive to failure by reason of notch effect than sheet copper without the phosphorus and said metal when subjected to the cyclic stresses caused by expansion and contraction of the roofing; the phosphorus being between 0.001 and 0.2%; the arsenic, if no antimony is present, be-

ing between 0.02 and 1.5%; the antimony, if no arsenic is present, being between 0.05 and 0.8%; and, if both arsenic and antimony are present, the arsenic being between 0.1 and 0.8% and the antimony between 0.05 and 0.4%.

2. Roofing comprising sheet copper presenting an extensive external roofing surface, the copper being alloyed with such amounts of phosphorus and metal of the group consisting of arsenic and antimony as will cause the formation on said surface when exposed to atmospheric corrosion of a self-healing, adherent, protective film of compound containing phosphorus and metal of said group, while rendering the sheet copper less sensitive to failure by reason of notch effect than sheet copper without the phosphorus and said metal when subjected to the cyclic stresses caused by expansion and contraction of the roofing; the phosphorus being between 0.001 and 0.2%; the arsenic, if no antimony is present, being between 0.02 and 1.5% the antimony, if no arsenic is present, being between 0.05 and 0.8%; and, if both arsenic and antimony are present, the arsenic being between 0.1 and 0.8% and the antimony between 0.05 and 0.4%, with the percentage of arsenic at least twice that of the antimony.

3. Roofing comprising sheet copper presenting an extensive external roofing surface, the copper being alloyed with such amounts of phosphorus and metal of the group consisting of arsenic and antimony as will cause the formation on said surface when exposed to atmospheric corrosion of a self-healing, adherent, protective film of compound containing phosphorus and metal of said group, while rendering the sheet copper less sensitive to failure by reason of notch effect than sheet copper without the phosphorus and said metal when subjected to the cyclic stresses caused by expansion and contraction of the roofing; the phosphorus being between 0.05 and 0.2%; the arsenic, if no antimony is present, being between 0.02 and 1.5%; the antimony, if no arsenic is present, being between 0.05 and 0.8%; and, if both arsenic and antimony are present, the arsenic being between 0.1 and 0.8% and the antimony between 0.05 and 0.4%.

4. Roofing comprising sheet copper presenting an extensive external roofing surface, the copper being alloyed with such amounts of phosphorus and metal of the group consisting of arsenic and antimony as will cause the formation on said surface when exposed to atmospheric corrosion of a self-healing, adherent, protective film of compound containing phosphorus and metal of said group, while rendering the sheet copper less sensitive to failure by reason of notch effect than sheet copper without the phosphorus and said metal when subjected to the cyclic stresses caused by expansion and contraction of the roofing; the phosphorus being between 0.05 and 0.2%; the arsenic, if no antimony is present, being between 0.02 and 1.5%; the antimony, if no arsenic is present, being between 0.05 and 0.8%; and, if both arsenic and antimony are present, the arsenic being between 0.1 and 0.8% and the antimony between 0.05 and 0.4%, with the percentage of arsenic at least twice that of the antimony.

5. Roofing comprising sheet copper presenting an extensive external roofing surface, the copper being alloyed with phosphorus and metal of the group consisting of arsenic and antimony; the phosphorus being between approximately 0.001 and 0.2%; the arsenic, if no antimony is present, being between approximately 0.02 and 1.5%

the antimony, if no arsenic is present, being between approximately 0.05 and 0.8% and, if both arsenic and antimony are present, the arsenic being between approximately 0.1 and 0.8% and the antimony between approximately 0.05 and 0.4%; the balance of the alloy with respect to the phosphorus and metal of said group being essentially copper.

6. Roofing comprising sheet copper presenting an extensive external roofing surface, the copper being alloyed with phosphorus and metal of the group consisting of arsenic and antimony; the phosphorus being between approximately 0.001 and 0.2%; the arsenic, if no antimony is present, being between approximately 0.02 and 1.5%; the antimony, if no arsenic is present, being between approximately 0.05 and 0.8%; and, if both arsenic and antimony are present, the arsenic being between approximately 0.1 and 0.3% and the antimony between approximately 0.05 and 0.4%, with the percentage of arsenic at least twice that of the antimony; the balance of the alloy with respect to the phosphorus and metal of said group being essentially copper.

'7. Roofing comprising sheet copper presenting an extensive external roofing surface, the copper being alloyed with phosphorus and metal of the group consisting of arsenic and antimony; the phosphorus being between approximately 0.05 and 0.2%; the arsenic, if no antimony is present, 2

being between approximately 0.02 and 1.5%; the antimony, if no arsenic is present, being between approximately 0.05 and 0.8%; and, if both arsenic and antimony are present, the arsenic being between approximately 0.1 and 0.8% and the antimony between approximately 0.05 and 0.4%; the balance of the alloy with respect to the phosphorus and metal of said group being essentially copper.

8. Roofing comprising sheet copper presenting an extensive external roofing surface, the copper being alloyed with phosphorus and metal of the group consisting of arsenic and antimony; the phosphorus being between approximately 0.05

and 0.2%; the arsenic, if no antimony is present, being between approximately 0.02 and 1.5%; the antimony, if no arsenic is present, being between approximately 0.05 and 0.8%; and, if both arsenic and antimony are present, the arsenic being between approximately 0.1 and 0.8% and the antimony between approximately 0.05 and 0.4%, with the percentage of arsenic at least twice that of the antimony; the balance of the alloy with respect to the phosphorus and metal of said group being essentially copper.

9. Roofing comprising sheet copper presenting an extensive external roofing surface, the copper being alloyed with phosphorus and metal of the group consisting of arsenic and antimony; the phosphorus being between approximately 0.05 and 0.15%; the arsenic, if no antimony is present, being between approximately 0.35 and 0.65%; the antimony, if no arsenic is present, being between approximately 0.05 and 0.8%; and, if 30th arsenic and antimony are present, the a senic being between approximately 0.4 and 0.6% and the antimony between approximately 0.2 and 0.3%; the balance of the alloy with respect to the phosphorus and metal of said group being essentially copper.

10. Roofing comprising sheet copper presenting an extensive external roofing surface, the copper being alloyed with phosphorus and metal of the group consisting of arsenic and antimony; the phosphorus being between approximately 0.05 and 0.15%; the arsenic, if no antimony is present, being between approximately 0.35 and 0.65%; the antimony, if no arsenic is present, being between approximately 0.05 and 0.8%; and. if both arsenic and antimony are present, the arsenic being between approximately 0.4 and 0.6% and the antimony between approximately 0.2 and 0.3%, with the pecentage of arsenic at least twice that of the antimony; the balance of the alloy with respect to the phosphorus and metal of said group being essentially copper.

RICHARD A. W'ILKINS. 

